Urethral meatal colonization in the pathogenesis of catheter-associated bacteriuria

Urethral meatal colonization with potential urinary tract pathogens was studied before bacteriuria in 31 consecutive acute spinal cord injury patients on an open ward (137 cultures) and 18 renal homotransplant patients in reverse isolation (80 cultures). All patients required indwelling urethral catheterization and no antimicrobials were given. Daily quantitative cultures of the urethral meatus, and bladder and drainage bag urine were obtained. The urethra was the source for 11 of 31 episodes of bacteriuria (35 per cent). Urethral meatal colonization with the organism responsible for bacteriuria, that is Escherichia coli (5 episodes), Staphylococcus aureus (2), Streptococcus faecalis (2) and Staphylococcus epidermidis (2), was persistent and present from 2 to 5 days before bacteriuria. In each ward 81 per cent or more of the cultures obtained on day 1 of catheterization showed no gram-negative colonization. Subsequently, the gram-negative colonization density increased in both groups but the increase was significant (p less than 0.001) only for patients on the open ward. Similar trends were observed for gram-positive colonization. The prevalence of potential pathogens was similar for patients whether or not they suffered bacteriuria. An increased density of bacterial colonization was associated with increased susceptibility to bacteriuria but the specific urethral meatal flora was not always predictive of the species responsible for bacteriuria.